A conventional plastic semiconductor package includes a semiconductor die attached to a segment of a leadframe, and encapsulated in a plastic body. One type of leadframe includes a mounting paddle that attaches to a backside of the die to support the die during encapsulation. The leadframe also includes lead fingers wire bonded to bond pads on the face of the die, then trimmed and formed into terminal leads for the package.
Another type of leadframe, known as a "lead-on-chip" (LOC) leadframe, includes lead fingers that attach directly to the face of the die to provide support during encapsulation, and the terminal leads for the package. Yet another type of leadframe comprises an organic polymer such as bismaleimide-triazine, epoxy or polyimide, reinforced with glass fibers.
In order to provide an increased circuit density and storage capability, a single semiconductor package can also include multiple semiconductor dice. For example, some semiconductor packages, known as "double die" packages, include two dice wired together with a common lead system. Other packages can include three, or sometimes more, semiconductor dice.
One consideration in fabricating multiple dice packages is heat transfer from the dice to the environment. With multiple dice contained in a package, at least twice the heat is generated during operation of the package. Some prior art multiple dice packages are not efficient in transferring heat generated by the dice. For example, packages that include organic lead frames, or lead frames with die mounting paddles, are generally not efficient at transferring and dissipating heat from the dice.
Another consideration in fabricating multiple dice packages is the efficiency of the fabrication process. Some packages require multiple encapsulation steps, which adds complexity to the fabrication process, and increases the expense of the packages. These fabrication processes can also require specialized equipment and materials.
In addition, multiple dice semiconductor packages having complex configurations may not be as reliable as conventional single die packages. In particular, the seal between the dice and package body can be compromised by the location and number of the parting lines between the dice and leadframe. Further, some multiple dice packages require complex wire bonding arrangements, such as relatively long length bond wires. These wire bonds can increase resistivity, generate parasitic signals, and adversely affect the reliability of the package.
The present invention is directed to a multiple dice semiconductor package having an efficient heat transfer path from the dice. In addition, the package has a simplified configuration, and can be fabricated using conventional equipment and materials.